[M4IF Technotes] hi

[Sudhakar Rao Kimidi]

Hi all,
With respect to discussions below about fixed interval synchronization ....
Gary,... you can find the maximum video packet size specified on the last
page on either of versions the satnadards ISO 14496-1 or 14496-2.
Now I have a doubt regarding the following line:
If the number of bits contained in the current video packet exceeds a
predetermined threshold, then a new video packet is created at the start of
the next macroblock.
===================================================
What is the value of the threshold? Has it been mentioned in the standard?
Or is this threshhold same as maximum video packet size.
====================================================
Gary Sullivan wrote:
> Reply interspersed:
>
> +> -----Original Message-----
> +> From: G Chandra Sekhar Reddy [mailto:gchandra   tataelxsi.co.in]
> +> Sent: Thursday, September 13, 2023 11:30 PM
> +> To: Jani Huoponen; Sudhakar Rao Kimidi; technotes   lists.m4if.org
> +> Subject: Re: [M4IF Technotes] hi
> +>
> +>
> [snip]
> +> The Levels restrict maximum number of bits per VideoPacket,
> +> making these
> +> synchronization points appear within some fixed interval
> +> (interval in bits,
> +> in bitstream).
>
> Are you sure about that statement?  I don't think it's true.
> Can you point to where such a restriction can be found?
>
> +> This is only restriction on the maximum size. The actual
> +> sizes (thereby
> +> synchronization intervals) can be less than this maximum size.
> +> If you want fixed size (thereby fixed synchronization
> +> intervals), you can
> +> use stuffing.
>
> I think you're right.  I guess some combination of MCBPC stuffing and
> bit stuffing can enable the encoder to hit any desired
> reasonably-large packet size.
>
> +> About the legal interval you are taking about, I think only
> +> restriction is
> +> that they shall be at BYTE-Boundaries.
>
> They also must start at macroblock boundaries.  Each packet must
> contain the bits to represent an integer number of macroblocks.
>
> +>
> +> Does the standard restrict VOP size in bits to some maximum
> +> value in any
> +> Profile / Level?
>
> Not that I'm aware of.
>
> +>
> +> Chandra
> +> *************************************************************
> +> *********
> +> Chandra Sekhar Reddy G.,
> +> TATA ELXSI Ltd.,
> +> WhiteField Road, Hoody,
> +> BANGALORE, INDIA - 560048.
> +> TEL: +91-80-8410148, 8411811, 8411812 (Ext:254),
> +> FAX: +91-80-8410152, 8411813.
> +> EMAIL: gchandra   tataelxsi.co.in
> +> WEB: www.tataelxsi.com
> +> *************************************************************
> +> *********
> +>
> +> ----- Original Message -----
> +> From: Jani Huoponen <Jani.Huoponen   hantro.com>
> +> To: Sudhakar Rao Kimidi <sudhakar   cradle.com>;
> +> <technotes   lists.m4if.org>
> +> Sent: Thursday, September 13, 2023 9:25 PM
> +> Subject: RE: [M4IF Technotes] hi
> +>
> +>
> +> > Dear Sudhakar,
> +> >
> +> > > Dear all,
> +> > >
> +> > > Can somebody help me with the answers for the following.
> +> > >
> +> > > 1. Which method of Quantization is used in MPEG-4 video
> +> > > simple profile?
> +> >
> +> > Type 2.
> +> >
> +> > > Are both methods of Quantizations used in MPEG-4 Video
> +> simple profile?
> +> >
> +> > No. Type 1 (quantization matrices) is not used in Simple profile.
> +> >
> +> > > 2. Is fixed interval synchronization supported in simple
> +> > > profile? Is it
> +> > > compulsory to use the method? Is there any mentioning about it in
> +> > > syntax?(This method requires that VOP start codes and
> +> > > resynchronization
> +> > > markers appear only at legal fixed interval locations in the
> +> > > bitstream)
> +> >
> +> > If you mean that should encoded VOPs have a fixed time
> +> interval between
> +> them
> +> > then the answer is yes. Simple profile supports this. See
> +> section 6.3.3.
> +> in
> +> > the 14496-2 standard, the field called "fixed_vop_rate"
> +> explains how this
> +> > works. It is not a compulsory method, i.e., VOPs can have
> +> variable time
> +> > intervals between them.
> +> >
> +> > BR, Jani
> +> >
> +> > ------------------------------------------------------------
> +> > Jani Huoponen
> +> > Engineering Manager, System Design
> +> > Hantro Products Oy
> +> > Nahkatehtaankatu 2, 90100 Oulu, Finland
> +> > +358-40-5272676
> +> > ------------------------------------------------------------
> +> >
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Thanks&Regards,
Sudhakar.